feat: replacing polling for lobby updates with LobbyEvents [MTT-5425] (#805)

* replacing polling for lobby updates with lobby events

* adding support for deleted lobby events

* updating to lobby 1.1.0-pre.3

* fixing issue with UpdateRunner using wrong dt when updating subscribers

* simplifying LobbyServiceFacade delete, leaveLobby and reconnect method calls

* Adding early return in reconnection when lobby is deleted

* removing GetLobby unused method

* Adding short delay before first reconnect attempt to give time for lobby to be properly updated

Co-authored-by: Sam Bellomo <[email protected]>

Author: LPLafontaineB

.yamato/mobile-build-and-run.yml

@@ -14,7 +14,7 @@ Build_Player_With_Tests_iOS_{{ project.name }}_{{ editor }}:
 
     commands:
         - pip install unity-downloader-cli==1.2.0 --index-url https://artifactory.prd.it.unity3d.com/artifactory/api/pypi/pypi/simple --upgrade
-        - unity-downloader-cli -c Editor -c iOS -u {{ editor }} --fast --wait
+        - unity-downloader-cli -c Editor -c iOS -u 2021.3.15f1 --fast --wait
         - curl -s https://artifactory.prd.it.unity3d.com/artifactory/unity-tools-local/utr-standalone/utr --output utr
         - chmod +x ./utr
         - ./utr --suite=playmode --platform=iOS --editor-location=.Editor --testproject={{ project.path }} --player-save-path=build/players --artifacts_path=build/logs --build-only --testfilter=Unity.BossRoom.Tests.Runtime

Assets/Scripts/ConnectionManagement/ConnectionMethod.cs

@@ -169,16 +169,9 @@ public override async Task SetupClientConnectionAsync()
             // some time to attempt to reconnect (defined by the "Disconnect removal time" parameter on the dashboard),
             // after which they will be removed from the lobby completely.
             // See https://docs.unity.com/lobby/reconnect-to-lobby.html
-            var lobby = await m_LobbyServiceFacade.ReconnectToLobbyAsync(m_LocalLobby.LobbyID);
+            var lobby = await m_LobbyServiceFacade.ReconnectToLobbyAsync();
             var success = lobby != null;
-            if (success)
-            {
-                Debug.Log("Successfully reconnected to Lobby.");
-            }
-            else
-            {
-                Debug.Log("Failed to reconnect to Lobby.");
-            }
+            Debug.Log(success ? "Successfully reconnected to Lobby." : "Failed to reconnect to Lobby.");
             return (success, true); // return a success if reconnecting to lobby returns a lobby
         }
 

Assets/Scripts/ConnectionManagement/ConnectionState/ClientReconnectingState.cs

@@ -21,6 +21,7 @@ class ClientReconnectingState : ClientConnectingState
         Coroutine m_ReconnectCoroutine;
         int m_NbAttempts;
 
+        const float k_TimeBeforeFirstAttempt = 1;
         const float k_TimeBetweenAttempts = 5;
 
         public override void Enter()
@@ -105,6 +106,15 @@ IEnumerator ReconnectCoroutine()
             yield return new WaitWhile(() => m_ConnectionManager.NetworkManager.ShutdownInProgress); // wait until NetworkManager completes shutting down
             Debug.Log($"Reconnecting attempt {m_NbAttempts + 1}/{m_ConnectionManager.NbReconnectAttempts}...");
             m_ReconnectMessagePublisher.Publish(new ReconnectMessage(m_NbAttempts, m_ConnectionManager.NbReconnectAttempts));
+
+            // If first attempt, wait some time before attempting to reconnect to give time to services to update
+            // (i.e. if in a Lobby and the host shuts down unexpectedly, this will give enough time for the lobby to be
+            // properly deleted so that we don't reconnect to an empty lobby
+            if (m_NbAttempts == 0)
+            {
+                yield return new WaitForSeconds(k_TimeBeforeFirstAttempt);
+            }
+
             m_NbAttempts++;
             var reconnectingSetupTask = m_ConnectionMethod.SetupClientReconnectionAsync();
             yield return new WaitUntil(() => reconnectingSetupTask.IsCompleted);

Assets/Scripts/Gameplay/UI/RoomNameBox.cs

@@ -22,12 +22,11 @@ private void InjectDependencies(LocalLobby localLobby)
         {
             m_LocalLobby = localLobby;
             m_LocalLobby.changed += UpdateUI;
-            UpdateUI(localLobby);
         }
 
         void Awake()
         {
-            gameObject.SetActive(false);
+            UpdateUI(m_LocalLobby);
         }
 
         private void OnDestroy()
@@ -44,6 +43,10 @@ private void UpdateUI(LocalLobby localLobby)
                 gameObject.SetActive(true);
                 m_CopyToClipboardButton.gameObject.SetActive(true);
             }
+            else
+            {
+                gameObject.SetActive(false);
+            }
         }
 
         public void CopyToClipboard()

Assets/Scripts/Infrastructure/UpdateRunner.cs

@@ -14,6 +14,7 @@ class SubscriberData
         {
             public float Period;
             public float NextCallTime;
+            public float LastCallTime;
         }
 
         readonly Queue<Action> m_PendingHandlers = new Queue<Action>();
@@ -56,7 +57,7 @@ public void Subscribe(Action<float> onUpdate, float updatePeriod)
                 {
                     if (m_Subscribers.Add(onUpdate))
                     {
-                        m_SubscriberData.Add(onUpdate, new SubscriberData() { Period = updatePeriod, NextCallTime = 0 });
+                        m_SubscriberData.Add(onUpdate, new SubscriberData() { Period = updatePeriod, NextCallTime = 0, LastCallTime = Time.time });
                     }
                 });
             }
@@ -90,7 +91,8 @@ void Update()
 
                 if (Time.time >= subscriberData.NextCallTime)
                 {
-                    subscriber.Invoke(Time.deltaTime);
+                    subscriber.Invoke(Time.time - subscriberData.LastCallTime);
+                    subscriberData.LastCallTime = Time.time;
                     subscriberData.NextCallTime = Time.time + subscriberData.Period;
                 }
             }

Assets/Scripts/UnityServices/Lobbies/LobbyAPIInterface.cs

@@ -107,11 +107,6 @@ public async Task<QueryResponse> QueryAllLobbies()
             return await LobbyService.Instance.QueryLobbiesAsync(queryOptions);
         }
 
-        public async Task<Lobby> GetLobby(string lobbyId)
-        {
-            return await LobbyService.Instance.GetLobbyAsync(lobbyId);
-        }
-
         public async Task<Lobby> UpdateLobby(string lobbyId, Dictionary<string, DataObject> data, bool shouldLock)
         {
             UpdateLobbyOptions updateOptions = new UpdateLobbyOptions { Data = data, IsLocked = shouldLock };
@@ -133,5 +128,10 @@ public async void SendHeartbeatPing(string lobbyId)
         {
             await LobbyService.Instance.SendHeartbeatPingAsync(lobbyId);
         }
+
+        public async Task<ILobbyEvents> SubscribeToLobby(string lobbyId, LobbyEventCallbacks eventCallbacks)
+        {
+            return await LobbyService.Instance.SubscribeToLobbyEventsAsync(lobbyId, eventCallbacks);
+        }
     }
 }

Assets/Scripts/UnityServices/Lobbies/LobbyServiceFacade.cs

@@ -37,8 +37,12 @@ public class LobbyServiceFacade : IDisposable, IStartable
 
         public Lobby CurrentUnityLobby { get; private set; }
 
+        ILobbyEvents m_LobbyEvents;
+
         bool m_IsTracking = false;
 
+        LobbyEventConnectionState m_LobbyEventConnectionState = LobbyEventConnectionState.Unknown;
+
         public void Start()
         {
             m_ServiceScope = m_ParentScope.CreateChild(builder =>
@@ -77,88 +81,29 @@ public void BeginTracking()
             if (!m_IsTracking)
             {
                 m_IsTracking = true;
-                // 2s update cadence is arbitrary and is here to demonstrate the fact that this update can be rather infrequent
-                // the actual rate limits are tracked via the RateLimitCooldown objects defined above
-                m_UpdateRunner.Subscribe(UpdateLobby, 2f);
+                SubscribeToJoinedLobbyAsync();
                 m_JoinedLobbyContentHeartbeat.BeginTracking();
             }
         }
 
-        public Task EndTracking()
+        public void EndTracking()
         {
-            var task = Task.CompletedTask;
             if (CurrentUnityLobby != null)
             {
-                CurrentUnityLobby = null;
-
-                var lobbyId = m_LocalLobby?.LobbyID;
-
-                if (!string.IsNullOrEmpty(lobbyId))
+                if (m_LocalUser.IsHost)
                 {
-                    if (m_LocalUser.IsHost)
-                    {
-                        task = DeleteLobbyAsync(lobbyId);
-                    }
-                    else
-                    {
-                        task = LeaveLobbyAsync(lobbyId);
-                    }
+                    DeleteLobbyAsync();
+                }
+                else
+                {
+                    LeaveLobbyAsync();
                 }
-
-                m_LocalUser.ResetState();
-                m_LocalLobby?.Reset(m_LocalUser);
             }
 
             if (m_IsTracking)
             {
-                m_UpdateRunner.Unsubscribe(UpdateLobby);
                 m_IsTracking = false;
-                m_HeartbeatTime = 0;
-                m_JoinedLobbyContentHeartbeat.EndTracking();
-            }
-
-            return task;
-        }
-
-        async void UpdateLobby(float unused)
-        {
-            if (!m_RateLimitQuery.CanCall)
-            {
-                return;
-            }
-
-            try
-            {
-                var lobby = await m_LobbyApiInterface.GetLobby(m_LocalLobby.LobbyID);
-
-                CurrentUnityLobby = lobby;
-                m_LocalLobby.ApplyRemoteData(lobby);
-
-                // as client, check if host is still in lobby
-                if (!m_LocalUser.IsHost)
-                {
-                    foreach (var lobbyUser in m_LocalLobby.LobbyUsers)
-                    {
-                        if (lobbyUser.Value.IsHost)
-                        {
-                            return;
-                        }
-                    }
-                    m_UnityServiceErrorMessagePub.Publish(new UnityServiceErrorMessage("Host left the lobby", "Disconnecting.", UnityServiceErrorMessage.Service.Lobby));
-                    await EndTracking();
-                    // no need to disconnect Netcode, it should already be handled by Netcode's callback to disconnect
-                }
-            }
-            catch (LobbyServiceException e)
-            {
-                if (e.Reason == LobbyExceptionReason.RateLimited)
-                {
-                    m_RateLimitQuery.PutOnCooldown();
-                }
-                else if (e.Reason != LobbyExceptionReason.LobbyNotFound && !m_LocalUser.IsHost) // If Lobby is not found and if we are not the host, it has already been deleted. No need to publish the error here.
-                {
-                    PublishError(e);
-                }
+                UnsubscribeToJoinedLobbyAsync();
             }
         }
 
@@ -264,6 +209,91 @@ async void UpdateLobby(float unused)
             return (false, null);
         }
 
+        void ResetLobby()
+        {
+            CurrentUnityLobby = null;
+            m_LocalUser.ResetState();
+            m_LocalLobby?.Reset(m_LocalUser);
+
+            // no need to disconnect Netcode, it should already be handled by Netcode's callback to disconnect
+        }
+
+        void OnLobbyChanges(ILobbyChanges changes)
+        {
+            if (changes.LobbyDeleted)
+            {
+                Debug.Log("Lobby deleted");
+                ResetLobby();
+            }
+            else
+            {
+                Debug.Log("Lobby updated");
+                changes.ApplyToLobby(CurrentUnityLobby);
+                m_LocalLobby.ApplyRemoteData(CurrentUnityLobby);
+
+                // as client, check if host is still in lobby
+                if (!m_LocalUser.IsHost)
+                {
+                    foreach (var lobbyUser in m_LocalLobby.LobbyUsers)
+                    {
+                        if (lobbyUser.Value.IsHost)
+                        {
+                            return;
+                        }
+                    }
+
+                    m_UnityServiceErrorMessagePub.Publish(new UnityServiceErrorMessage("Host left the lobby", "Disconnecting.", UnityServiceErrorMessage.Service.Lobby));
+                    EndTracking();
+                    // no need to disconnect Netcode, it should already be handled by Netcode's callback to disconnect
+                }
+            }
+        }
+
+        void OnKickedFromLobby()
+        {
+            Debug.Log("Kicked from Lobby");
+            ResetLobby();
+        }
+
+        void OnLobbyEventConnectionStateChanged(LobbyEventConnectionState lobbyEventConnectionState)
+        {
+            m_LobbyEventConnectionState = lobbyEventConnectionState;
+            Debug.Log($"LobbyEventConnectionState changed to {lobbyEventConnectionState}");
+        }
+
+        async void SubscribeToJoinedLobbyAsync()
+        {
+            var lobbyEventCallbacks = new LobbyEventCallbacks();
+            lobbyEventCallbacks.LobbyChanged += OnLobbyChanges;
+            lobbyEventCallbacks.KickedFromLobby += OnKickedFromLobby;
+            lobbyEventCallbacks.LobbyEventConnectionStateChanged += OnLobbyEventConnectionStateChanged;
+            // The LobbyEventCallbacks object created here will now be managed by the Lobby SDK. The callbacks will be
+            // unsubscribed from when we call UnsubscribeAsync on the ILobbyEvents object we receive and store here.
+            m_LobbyEvents = await m_LobbyApiInterface.SubscribeToLobby(m_LocalLobby.LobbyID, lobbyEventCallbacks);
+            m_JoinedLobbyContentHeartbeat.BeginTracking();
+        }
+
+        async void UnsubscribeToJoinedLobbyAsync()
+        {
+            if (m_LobbyEvents != null && m_LobbyEventConnectionState != LobbyEventConnectionState.Unsubscribed)
+            {
+                try
+                {
+                    await m_LobbyEvents.UnsubscribeAsync();
+                }
+                catch (ObjectDisposedException e)
+                {
+                    // This exception occurs in the editor when exiting play mode without first leaving the lobby.
+                    // This is because Wire disposes of subscriptions internally when exiting play mode in the editor.
+                    Debug.Log("Subscription is already disposed of, cannot unsubscribe.");
+                    Debug.Log(e.Message);
+                }
+
+            }
+            m_HeartbeatTime = 0;
+            m_JoinedLobbyContentHeartbeat.EndTracking();
+        }
+
         /// <summary>
         /// Used for getting the list of all active lobbies, without needing full info for each.
         /// </summary>
@@ -293,11 +323,11 @@ public async Task RetrieveAndPublishLobbyListAsync()
             }
         }
 
-        public async Task<Lobby> ReconnectToLobbyAsync(string lobbyId)
+        public async Task<Lobby> ReconnectToLobbyAsync()
         {
             try
             {
-                return await m_LobbyApiInterface.ReconnectToLobby(lobbyId);
+                return await m_LobbyApiInterface.ReconnectToLobby(m_LocalLobby.LobbyID);
             }
             catch (LobbyServiceException e)
             {
@@ -314,12 +344,13 @@ public async Task<Lobby> ReconnectToLobbyAsync(string lobbyId)
         /// <summary>
         /// Attempt to leave a lobby
         /// </summary>
-        public async Task LeaveLobbyAsync(string lobbyId)
+        public async void LeaveLobbyAsync()
         {
             string uasId = AuthenticationService.Instance.PlayerId;
             try
             {
-                await m_LobbyApiInterface.RemovePlayerFromLobby(uasId, lobbyId);
+                await m_LobbyApiInterface.RemovePlayerFromLobby(uasId, m_LocalLobby.LobbyID);
+                ResetLobby();
             }
             catch (LobbyServiceException e)
             {
@@ -351,13 +382,14 @@ public async void RemovePlayerFromLobbyAsync(string uasId, string lobbyId)
             }
         }
 
-        public async Task DeleteLobbyAsync(string lobbyId)
+        public async void DeleteLobbyAsync()
         {
             if (m_LocalUser.IsHost)
             {
                 try
                 {
-                    await m_LobbyApiInterface.DeleteLobby(lobbyId);
+                    await m_LobbyApiInterface.DeleteLobby(m_LocalLobby.LobbyID);
+                    ResetLobby();
                 }
                 catch (LobbyServiceException e)
                 {

CHANGELOG.md

@@ -7,6 +7,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 Additional documentation and release notes are available at [Multiplayer Documentation](https://docs-multiplayer.unity3d.com).
 
 ## [unreleased] - yyyy-mm-dd
+
+### Changed
+* Replaced our polling for lobby updates with a subscription to the new Websocket based LobbyEvents (#805). This saves up a significant amount of bandwidth usage to and from the service, since updates are infrequent in this game. Now clients and hosts only use up bandwidth on the Lobby service when it is needed. With polling, we used to send a GET request per client once every 2s. The responses were between ~550 bytes and 900 bytes, so if we suppose an average of 725 bytes and 100 000 concurrent users (CCU), this amounted to around 725B * 30 calls per minute * 100 000 CCU = 2.175 GB per minute. Scaling this to a month would get us 93.96 TB per month. In our case, since the only changes to the lobbies happen when a user connects or disconnects, most of that data was not necessary and can be saved to reduce bandwidth usage. Since the cost of using the Lobby service depends on bandwidth usage, this would also save money on an actual game.
+* 
 ### Cleanup
 * Clarified a TODO comment inside ClientCharacter, detailing how anticipation should only be executed on owning client players (#786)
 * Removed now unnecessary cached NetworkBehaviour status on some components, since they now do not allocate memory (#799)
@@ -18,6 +22,7 @@ Additional documentation and release notes are available at [Multiplayer Documen
 * EnemyPortals' VFX get disabled and re-enabled once the breakable crystals are broken (#784)
 * Elements inside the Tank's and Rogue's AnimatorTriggeredSpecialFX list have been revised to not loop AudioSource clips, ending the logging of multiple warnings to the console (#785)
 * ClientConnectedState now inherits from OnlineState instead of the base ConnectionState (#801)
+* UpdateRunner now sends the right value for deltaTime when updating its subscribers (#805)
 
 ## [2.0.4] - 2022-12-13
 ### Changed